Opalizing cousin quince (Doryteuthis opalescens) is one of the most sophisticated shape shifters on earth. These curious skulls are encased in a special skin that can be precisely tuned to a color scoop of color.
Scientists have long been fascinated by the remarkable camouflage and communication of this squid. New research has brought us even closer to finding out how they can pull out such an eclectic wardrobe that allows them to hunt near the brightness of the shore, by sliding unseen predators, or even evading aggressive suitors by ‘ to flick some fake testes.
Previous studies have shown that the opalescent squid has a complex molecular machine in its skin: a thin film of stacked cells that can expand and contract like an accordion to reflect the entire visible light spectrum, from red and orange to yellow and green , to blue. and violet.
These small grooves are similar to what you see on a compact disc, say researchers, and reflect a rainbow of colors as you tilt it under the light. But just like a CD, this skin also needs something to enhance its colorful noise.
When researchers genetically engineered this squid’s skin, they noticed that something was slightly off.
The ‘motor’ that tunes the grooves in the squid’s skin is powered by reflective proteins, which respond to different neural signals and control reflective pigment cells.
Synthetic materials containing reflectin proteins have an iridescent appearance as in squid, but these materials could not flicker or shine in the same way.
Something was clearly missing, and recent studies on live squid and genetic engineering have shed light on the mystery. It appears that reflectin proteins can only shine brightly when wrapped in a reflective membrane envelope.
This envelope includes the accordion-like structure, and at the bottom you can see how it works.
Reflective proteins are usually repelled by each other, but a neuronal signal from the squid’s brain can switch off the positive charge, which can cause the proteins to clump together.
When this happens, it causes the overlying membrane to push water out of the cell, shrinking the thickness and spacing of the grooves, dividing light into different colors.
This collapse between the grooves also increases the concentration of reflection, which makes the light reflect even brighter.
So, the authors explain, this complex process “dynamically [tunes] the color while increasing the reflection light at the same time “, and this is what makes the opalescent squid flicker and flicker, sometimes with color and sometimes not.
Cells in the squid’s skin, which reflect only white light, also appear to be driven by the same molecular mechanism. In fact, the authors think it could mimic the squid the glittering or mottled light of the sun on waves.
“Evolution has not only optimized color tuning so beautifully, but also the clarity of the same material, the same protein, and the same mechanism,” says biochemist Daniel Morse of the University of California, Santa Barbara.
Engineers have been trying for years to mimic the opalescent squid’s remarkable skin, but have never gotten there. The new research, supported by the US Army Office, helped us figure out where we were going wrong.
In the end, thin reflective films may not provide the full power control we see in squid, the authors conclude, because we do not seem to lack the coupled amplifier.
“Without the membrane around the reflectors, there is no change in the brightness of these artificially thin films,” says Morse.
“If we want to capture the power of the biological, we need to include a kind of membrane-like sheath to adjust the brightness reversibly.”
The study was published in Applied Physics Letters.